1. Field of the Invention
The present invention relates to a pneumatic tire in which a tread portion has longitudinal grooves extending in a circumferential direction of the tire and transverse grooves extending in a width direction of the tire formed therein and a plurality of land portions are formed by the longitudinal grooves and the transverse grooves.
The present invention claims priority from Japanese Patent Application No. 2007-281660 filed on Oct. 30, 2007, which is hereby incorporated by reference herein.
2. Background Art
In this type of the pneumatic tire, hitherto, for example, as indicated in Patent Citation 1 as described, by making the positions of the transverse grooves in the circumferential direction of the tire, which are adjacent to each other in a width direction of the tire, different from each other, an increase in deformation such as a mutual collapse of each of land portions adjacent to each other in the width direction of the tire is prevented in order to suppress an occurrence of noise.
Herein, in general, in order to improve tire performance when wet, it is known that a so-called edge effect is enhanced by making the size of the land portion smaller in order to increase number of edges of the land portion, which are caught on a road surface, on a contact area. In addition, it is known that among the plurality of land portions formed in the tread portion, the land portions situated at either side of the width direction of the tire in the tread portion greatly contribute to an improvement in tire performance when wet.
[Patent Citation 1] Specification of Japanese Patent Application Laid-Open Publication No. 9-188110
However, if the size of the land portion is made small in order to improve tire performance when wet, there is a problem that noise easily generated because the distance between each of the transverse grooves, which are adjacent to each other in the width direction of the tire, are shortened in the circumferential direction of the tire.
Herein, in a pneumatic tire having low-profile with a small outer diameter, since a ground contact length along the circumferential direction of the tire becomes short, the tier performance when wet cannot be maintained unless the size of the land portion is made to be smaller. On the other hand, if the size of the land portion is made to be smaller in this manner, since the distances between each of the transverse grooves in the circumferential direction of the tire, which are adjacent to each other in the width direction of the tire, become shortened and noise easily generated, the above-mentioned problem arises.